Rheumatoid arthritis (RA), a chronic autoimmune disorder, is characterized by inflammation of synovial joints and is mainly diagnosed through clinical manifestations and the presence of serological markers (RF and ACPA). However, approximately one third of the established RA patients are seronegative for both RA disease markers and the sensitivity of these markers is proven to be even lower in the early disease phase. Therefore, there is a need for additional RA disease markers in order to diagnose undifferentiated arthritis patients, early and seronegative RA patients.
Novel candidate autoantibody markers for early and seronegative RA patients were identified during a previous study by our research group. From these candidate markers, the antibody response directed against UH-RA.21 had the highest sensitivity (29%) and an associated specificity of 95% for RA. UH-RA.21 is a mimotope and contains an epitope that mimics an in vivo antigen. Both, the epitope and the identity of the in v